diff --git a/include/xo/gc/DX1Collector.hpp b/include/xo/gc/DX1Collector.hpp
index c5b8483..bd9d5a6 100644
--- a/include/xo/gc/DX1Collector.hpp
+++ b/include/xo/gc/DX1Collector.hpp
@@ -155,6 +155,7 @@ namespace xo {
         // ----- DX1Collector -----
 
         struct DX1Collector {
+            using typeseq = xo::facet::typeseq;
             using size_type = DArena::size_type;
             using value_type = DArena::value_type;
             using header_type = DArena::header_type;
@@ -216,9 +217,14 @@ namespace xo {
 
             // ----- allocation -----
 
-            /** simple allocation. new allocs always in gen0 to-space **/
-            value_type alloc(size_type z) noexcept;
-            /** compound allocation. To be followed immediately by:
+            /** simple allocation. allocate @p z bytes of memory
+             *  for an object of type @p t.
+             *  New allocs always in gen0 to-space
+             **/
+            value_type alloc(typeseq t, size_type z) noexcept;
+            /** compound allocation. Allocate @p z bytes of memory
+             *  for an object of type @p t.
+             *  To be followed immediately by:
              *  1. zero or more calls to sub_alloc(zi, complete=false), then
              *  2. exactly one call to sub_alloc(zi, complete=true)
              *  all the allocs in a compound allocation share the same
@@ -226,7 +232,7 @@ namespace xo {
              *  allocation with size z + sum(zi).
              *  New allocs always in gen0 to-space
              **/
-            value_type super_alloc(size_type z) noexcept;
+            value_type super_alloc(typeseq t, size_type z) noexcept;
             /** sub-allocation with preceding compound allocation.
              *  New allocs always in gen0 to-space
              **/
diff --git a/include/xo/gc/detail/IAllocator_DX1Collector.hpp b/include/xo/gc/detail/IAllocator_DX1Collector.hpp
index c525dad..6ba79b5 100644
--- a/include/xo/gc/detail/IAllocator_DX1Collector.hpp
+++ b/include/xo/gc/detail/IAllocator_DX1Collector.hpp
@@ -29,6 +29,7 @@ namespace xo {
          *  RAllocator      RCollector.hpp
          */
         struct IAllocator_DX1Collector {
+            using typeseq = xo::facet::typeseq;
             using size_type = std::size_t;
             using value_type = std::byte *;
             using range_type = AAllocator::range_type;
@@ -58,8 +59,8 @@ namespace xo {
             static range_type alloc_range(const DX1Collector & d, DArena & ialloc) noexcept;
 
             /** always alloc in gen0 to-space **/
-            static value_type alloc(DX1Collector & d, size_type z) noexcept;
-            static value_type super_alloc(DX1Collector & d, size_type z) noexcept;
+            static value_type alloc(DX1Collector & d, typeseq t, size_type z) noexcept;
+            static value_type super_alloc(DX1Collector & d, typeseq t, size_type z) noexcept;
             static value_type sub_alloc(DX1Collector & d, size_type z, bool complete) noexcept;
             /** expand gen0 spaces (both from-space and to-space) **/
             static bool expand(DX1Collector & d, size_type z) noexcept;
diff --git a/src/gc/DX1Collector.cpp b/src/gc/DX1Collector.cpp
index de74776..26223b9 100644
--- a/src/gc/DX1Collector.cpp
+++ b/src/gc/DX1Collector.cpp
@@ -216,14 +216,14 @@ namespace xo {
         }
 
         auto
-        DX1Collector::alloc(size_type z) noexcept -> value_type
+        DX1Collector::alloc(typeseq t, size_type z) noexcept -> value_type
         {
-            return with_facet<AAllocator>::mkobj(new_space()).alloc(z);
+            return with_facet<AAllocator>::mkobj(new_space()).alloc(t, z);
         }
 
         auto
-        DX1Collector::super_alloc(size_type z) noexcept -> value_type {
-            return with_facet<AAllocator>::mkobj(new_space()).super_alloc(z);
+        DX1Collector::super_alloc(typeseq t, size_type z) noexcept -> value_type {
+            return with_facet<AAllocator>::mkobj(new_space()).super_alloc(t, z);
         }
 
         auto
diff --git a/src/gc/IAllocator_DX1Collector.cpp b/src/gc/IAllocator_DX1Collector.cpp
index d3e172f..b5b26b5 100644
--- a/src/gc/IAllocator_DX1Collector.cpp
+++ b/src/gc/IAllocator_DX1Collector.cpp
@@ -12,6 +12,7 @@
 
 namespace xo {
     using xo::facet::with_facet;
+    using xo::facet::typeseq;
     using std::size_t;
     using std::byte;
 
@@ -80,15 +81,19 @@ namespace xo {
         }
 
         auto
-        IAllocator_DX1Collector::alloc(DX1Collector & d, size_type z) noexcept -> value_type
+        IAllocator_DX1Collector::alloc(DX1Collector & d,
+                                       typeseq t,
+                                       size_type z) noexcept -> value_type
         {
-            return d.alloc(z);
+            return d.alloc(t, z);
         }
 
         auto
-        IAllocator_DX1Collector::super_alloc(DX1Collector & d, size_type z) noexcept -> value_type
+        IAllocator_DX1Collector::super_alloc(DX1Collector & d,
+                                             typeseq t,
+                                             size_type z) noexcept -> value_type
         {
-            return d.super_alloc(z);
+            return d.super_alloc(t, z);
         }
 
         auto
diff --git a/utest/DX1CollectorIterator.test.cpp b/utest/DX1CollectorIterator.test.cpp
index ba3ba09..58a498c 100644
--- a/utest/DX1CollectorIterator.test.cpp
+++ b/utest/DX1CollectorIterator.test.cpp
@@ -30,6 +30,7 @@ namespace xo {
     using xo::mm::cmpresult;
     using xo::mm::padding;
     using xo::facet::with_facet;
+    using xo::facet::typeseq;
     using std::byte;
 
     namespace ut {
@@ -109,7 +110,7 @@ namespace xo {
             REQUIRE(a1o.allocated() == 0);
 
             size_t req_z = 13;
-            byte * mem = gc.alloc(req_z);
+            byte * mem = gc.alloc(typeseq::anon(), req_z);
 
             REQUIRE(mem != nullptr);
 
diff --git a/utest/random_allocs.cpp b/utest/random_allocs.cpp
index 4031534..654c6c9 100644
--- a/utest/random_allocs.cpp
+++ b/utest/random_allocs.cpp
@@ -43,6 +43,8 @@ namespace utest {
                              xoshiro256ss * p_rgen,
                              obj<AAllocator> mm)
     {
+        using xo::facet::typeseq;
+
         scope log(XO_DEBUG(catch_flag), xtag("n-alloc", n_alloc));
 
         /* track allocs. verify:
@@ -65,7 +67,7 @@ namespace utest {
 
             bool ok_flag = true;
 
-            std::byte * mem = mm.alloc(z);
+            std::byte * mem = mm.alloc(typeseq::anon(), z);
 
             log && log(xtag("i_alloc", i_alloc),
                        xtag("si", si),